Autodetection howto

Autodetection howto

[Tim Harvey]

Greetings,

I've got a 4-disk RAID5 array that I'm able to manually assemble and
mount, however I can't figure out how to get the autodetection to work.
In reading the Linux Software RAID howto it seems like it should 'just
work', but I'm running into a snag which doesn't seem to be described in
the HOWTO/FAQ.

The commands that I use to manually assemble and run my XFS filesystem
via LVM over RAID5 are:

# mdadm --assemble --run /dev/md0 /dev/hdb1 /dev/hdc1 /dev/hdd1
mdadm: /dev/md0 has been started with 3 drives (out of 4).
# mdadm --assemble --run /dev/md1 /dev/hdb3 /dev/hdc3 /dev/hdd3
mdadm: /dev/md1 has been started with 3 drives (out of 4).

Then for LVM:

# vgscan
# vgchange -a y
# mount -t xfs -o logdev=/dev/logdev/storage1 /dev/vgroup00/storage1
/mnt/data

Here are my log messages from bootup:

Jun 15 11:31:24 localhost kernel: md: autorun ...
Jun 15 11:31:24 localhost kernel: md: considering hdh1 ...
Jun 15 11:31:24 localhost kernel: md:  adding hdh1 ...
Jun 15 11:31:24 localhost kernel: md:  adding hdg1 ...
Jun 15 11:31:24 localhost kernel: md:  adding hdf1 ...
Jun 15 11:31:24 localhost kernel: md:  adding hde1 ...
Jun 15 11:31:24 localhost kernel: md: created md0
Jun 15 11:31:24 localhost kernel: md: bind<hde1,1>
Jun 15 11:31:24 localhost kernel: md: bind<hdf1,2>
Jun 15 11:31:24 localhost kernel: md: bind<hdg1,3>
Jun 15 11:31:24 localhost kernel: md: bind<hdh1,4>
Jun 15 11:31:25 localhost kernel: md: running: <hdh1><hdg1><hdf1><hde1>
Jun 15 11:31:25 localhost kernel: md: hdh1's event counter: 00000028
Jun 15 11:31:25 localhost kernel: md: hdg1's event counter: 00000028
Jun 15 11:31:25 localhost kernel: md: hdf1's event counter: 00000028
Jun 15 11:31:25 localhost kernel: md: hde1's event counter: 00000028
Jun 15 11:31:25 localhost kernel: kmod: failed to exec /sbin/modprobe -s
-k md-personality-4, errno = 2
Jun 15 11:31:25 localhost kernel: md: personality 4 is not loaded!
Jun 15 11:31:25 localhost kernel: md :do_md_run() returned -22
Jun 15 11:31:25 localhost kernel: md: md0 stopped.
Jun 15 11:31:25 localhost kernel: md: unbind<hdh1,3>
Jun 15 11:31:25 localhost kernel: md: export_rdev(hdh1)
Jun 15 11:31:25 localhost kernel: md: unbind<hdg1,2>
Jun 15 11:31:25 localhost kernel: md: export_rdev(hdg1)
Jun 15 11:31:25 localhost kernel: md: unbind<hdf1,1>
Jun 15 11:31:25 localhost kernel: md: export_rdev(hdf1)
Jun 15 11:31:25 localhost kernel: md: unbind<hde1,0>
Jun 15 11:31:25 localhost kernel: md: export_rdev(hde1)
Jun 15 11:31:25 localhost kernel: md: ... autorun DONE.

I'm not sure why I'm getting 'md: personality 4 is not loaded!', would
it be because RAID5 is loaded as a module instead of compiled into the
kernel?  I googled this and have added the following to
/etc/modules.conf and rebooted, but it did not change things:

# RAID autoload modules
alias md-personality-3 raid1
alias md-personality-4 raid5


Questions:

- How do I get around the 'personality 4 is not loaded'?  Did I need to
run something after I modified /etc/modules.conf for it to take effect?
- It would appear that the mounting of filesystems via /etc/fstab occurs
before md autoscans.  How can I delay the mounting of the filesystem
that exists on the RAID5 array?

Thanks for any help!

Tim

Re: Autodetection howto

[danci]

On Tue, 15 Jun 2004, Tim Harvey wrote:

> Greetings,
> 
> I've got a 4-disk RAID5 array that I'm able to manually assemble and
> mount, however I can't figure out how to get the autodetection to work.
> In reading the Linux Software RAID howto it seems like it should 'just
> work', but I'm running into a snag which doesn't seem to be described in
> the HOWTO/FAQ.

> - How do I get around the 'personality 4 is not loaded'?  Did I need to
> run something after I modified /etc/modules.conf for it to take effect?
> - It would appear that the mounting of filesystems via /etc/fstab occurs
> before md autoscans.  How can I delay the mounting of the filesystem
> that exists on the RAID5 array?


1. You need to set the partition that are in the array to the correct
   partition type - fd.

2. If you have raid compiled as modules, you need a proper initrd which
   will load appropriate modules (raid5) and then re-autodetect the arrays
   (SuSE uses 'raidautorun' for that) - all that before your OS actually
   starts booting.

As far as 'personality 4 is not loaded' - I think you don't need to worry 
about it. It just tells you that it's not loaded...

 D.

RE: Autodetection howto

[Tim Harvey]

> -----Original Message-----
> From: linux-raid-owner@vger.kernel.org [mailto:linux-raid-
> owner@vger.kernel.org] On Behalf Of danci@agenda.si
> Sent: Tuesday, June 15, 2004 11:35 PM
> To: Tim Harvey
> Cc: linux-raid@vger.kernel.org
> Subject: Re: Autodetection howto
> 
> On Tue, 15 Jun 2004, Tim Harvey wrote:
> 
> > Greetings,
> >
> > I've got a 4-disk RAID5 array that I'm able to manually assemble and
> > mount, however I can't figure out how to get the autodetection to
work.
> > In reading the Linux Software RAID howto it seems like it should
'just
> > work', but I'm running into a snag which doesn't seem to be
described in
> > the HOWTO/FAQ.
> 
> > - How do I get around the 'personality 4 is not loaded'?  Did I need
to
> > run something after I modified /etc/modules.conf for it to take
effect?
> > - It would appear that the mounting of filesystems via /etc/fstab
occurs
> > before md autoscans.  How can I delay the mounting of the filesystem
> > that exists on the RAID5 array?
> 
> 
> 1. You need to set the partition that are in the array to the correct
>    partition type - fd.
> 

Got this covered, and md is creating the array(s)... just still failing
with the 'md-personality' error which would seem to be why I need your
second step:

> 2. If you have raid compiled as modules, you need a proper initrd
which
>    will load appropriate modules (raid5) and then re-autodetect the
arrays
>    (SuSE uses 'raidautorun' for that) - all that before your OS
actually
>    starts booting.

I'm not exactly sure how to do this... could you give me an example?  My
existing initrd is /boot/initrd-2.4.22-1.2140.nptl_30.rhfc1.at.img so
I'm attempting:

# mkinitrd --preload raid5.o
/boot/initrd-2.4.22-1.2140.nptl_30.rhfc1.at.img 2.4.22-1

I'm getting a usage error and I'm evidently not understanding mkinitrd's
man page.

Thanks for your help,

Tim

> 
> As far as 'personality 4 is not loaded' - I think you don't need to
worry
> about it. It just tells you that it's not loaded...
> 
>  D.
> 
> -
> To unsubscribe from this list: send the line "unsubscribe linux-raid"
in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html

RE: Autodetection howto

[danci]

> > 2. If you have raid compiled as modules, you need a proper initrd
> >    which will load appropriate modules (raid5) and then re-autodetect
> >    the arrays (SuSE uses 'raidautorun' for that) - all that before
> >    your OS actually starts booting.

> I'm not exactly sure how to do this... could you give me an example?  
> My existing initrd is /boot/initrd-2.4.22-1.2140.nptl_30.rhfc1.at.img so
> I'm attempting:
> 
> # mkinitrd --preload raid5.o
> /boot/initrd-2.4.22-1.2140.nptl_30.rhfc1.at.img 2.4.22-1
> 
> I'm getting a usage error and I'm evidently not understanding mkinitrd's
> man page.

mkinitrd is pretty much distribution specific, so I cannot help you much
with that.

However, according to man page on Redhat 7.2 AXP that I have access to,
the 'mkinitrd' script is supposed to add raid modules automatically if the
system's root partition is on raid (I suppose it checks the /etc/fstab and 
/etc/raidtab files)...

Maybe you should check the content of your initrd by:

1. cp /boot/initrd-2.4.22-1.2140.nptl_30.rhfc1.at.img /tmp/myinitrd.gz
2. gunzip /tmp/myinitrd.gz
3. mkdir /tmp/loop
4. mount -o loop /tmp/myinitrd /tmp/loop
5. cd /tmp/loop

Here you will see a 'linuxrc' script, which lists all the commands that 
are executed.

This is my 'linuxrc':

#!/bin/nash

echo "Loading jbd module"
insmod /lib/jbd.o
echo "Loading ext3 module"
insmod /lib/ext3.o
mount -t proc /proc /proc
echo Mounting /proc filesystem
echo Creating root device
mkrootdev /dev/root
echo 0x0100 > /proc/sys/kernel/real-root-dev
umount /proc
echo Mounting root filesystem
mount --ro -t ext3 /dev/root /sysroot
pivot_root /sysroot /sysroot/initrd

As you can see, I don't use root on raid on this particular machine.

  D.